Nuclei | Class 12 Physics Notes
By ConceptScroll Team · Published on 17 July 2026 · 2 min read
Nuclei – this guide gives you a concise, exam-ready overview of Nuclei from Class 12 Physics, written by ConceptScroll editors and reviewed against the latest NCERT textbook.
13.7 NUCLEAR ENERGY
This section discusses the origin of nuclear energy based on the binding energy per nucleon curve. The curve is nearly flat between mass numbers A = 30 and 170, with binding energy per nucleon around 8 MeV, indicating maximum nuclear stability. For lighter nuclei (A < 30) and heavier nuclei (A > 170), the binding energy per nucleon is lower. Energy is released when nuclei with lower binding energy per nucleon transform into nuclei with higher binding energy per nucleon. This occurs in nuclear fission, where a heavy nucleus splits into intermediate mass fragments, and in nuclear fusion, where light nuclei combine to form heavier nuclei. Nuclear reactions release energy millions of times greater than chemical reactions. For example, fission of 1 kg of uranium produces about 10^14 J of energy, compared to 10^7 J from burning 1 kg of coal. The section introduces neutron-induced fission reactions of uranium-235, showing typical fission products and neutron emission. The energy released per fission is about 200 MeV. The section also explains nuclear fusion reactions, such as proton-proton fusion in stars, which produce helium and release energy. Fusion requires overcoming the Coulomb barrier, necessitating very high temperatures (thermonuclear fusion). The sun's core temperature (~1.5 × 10^7 K) allows fusion via high-energy protons above average energy. Controlled thermonuclear fusion aims to replicate these processes on Earth to generate power. The section concludes with a solved example addressing nuclear reaction equations and mass-energy conservation.
🔗 Connection: Leads to the summary section consolidating key points of the chapter.
Frequently asked questions
When a nucleus in an atom undergoes a radioactive decay, the electronic energy levels of the atom
change for α and β radioactivity but not for gamma-radioactivity.
Heavy stable nuclei have more neutrons than protons. This is because of the fact that
electrostatic forces between protons are repulsive
Which of the following statements is true for nuclear forces?
They are short-range forces
Nuclides with same neutron number N but different atomic Number Z, are called
Isotones
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